What is the best antibiotic for treating Moraxella (Moraxella catarrhalis) infections?

From the Guidelines

Amoxicillin with clavulanic acid 625 mg three times a day for 14 days is the recommended first-line treatment for Moraxella catarrhalis infections. This recommendation is based on the British Thoracic Society guideline for bronchiectasis in adults, published in 2019 1. The guideline suggests that Moraxella catarrhalis is commonly associated with acute exacerbation of bronchiectasis and that amoxicillin with clavulanic acid is the preferred first-line treatment due to its effectiveness against beta-lactamase-producing strains of the bacteria.

Some key points to consider when treating Moraxella catarrhalis infections include:

• The importance of completing the full prescribed course of antibiotics to prevent recurrence and antibiotic resistance
• The need to consider alternative treatments for patients with penicillin allergies, such as clarithromycin 500 mg twice daily for 14 days, doxycycline 100 mg twice daily for 14 days, or ciprofloxacin 500 mg or 750 mg twice daily for 14 days, as listed in the guideline 1
• The potential for severe infections to require initial intravenous therapy before transitioning to oral antibiotics

It is essential to note that the choice of antibiotic should be guided by the site of infection, with respiratory tract infections being the most common. The guideline provides a comprehensive list of recommended antimicrobial agents for various organisms associated with acute exacerbation of bronchiectasis, including Moraxella catarrhalis 1.

From the FDA Drug Label

1.1 Lower Respiratory Tract Infections – caused by beta-lactamase–producing isolates of Haemophilus influenzae and Moraxella catarrhalis. 1.2 Acute Bacterial Otitis Media – caused by beta-lactamase–producing isolates of H. influenzae and M. catarrhalis. 1.3 Sinusitis – caused by beta-lactamase–producing isolates of H. influenzae and M. catarrhalis. 1.1 Nosocomial Pneumonia Levofloxacin tablets are indicated for the treatment of nosocomial pneumonia due to methicillin-susceptible Staphylococcus aureus, Pseudomonas aeruginosa, Serratia marcescens, Escherichia coli, Klebsiella pneumoniae, Haemophilus influenzae, or Streptococcus pneumoniae. 1.2 Community-Acquired Pneumonia: 7 to 14 Day Treatment Regimen Levofloxacin tablets are indicated for the treatment of community-acquired pneumonia due to methicillin-susceptible Staphylococcus aureus, Streptococcus pneumoniae (including multi-drug-resistant Streptococcus pneumoniae [MDRSP]), Haemophilus influenzae, Haemophilus parainfluenzae, Klebsiella pneumoniae, Moraxella catarrhalis, Chlamydophila pneumoniae, Legionella pneumophila, or Mycoplasma pneumoniae. Presumed Bacteriologic Eradication Day 11Day 30 AzithromycinAzithromycin S. pneumoniae61/74 (82%)40/56 (71%) H. influenzae43/54 (80%)30/47 (64%) M. catarrhalis28/35 (80%)19/26 (73%)

The best antibiotic for Moraxella catarrhalis is not explicitly stated in the provided drug labels, but based on the indications,

• amoxicillin-clavulanate 2 is effective against beta-lactamase–producing isolates of Moraxella catarrhalis in lower respiratory tract infections, acute bacterial otitis media, and sinusitis.
• levofloxacin 3 is effective against Moraxella catarrhalis in community-acquired pneumonia and acute bacterial sinusitis.
• azithromycin 4 has shown effectiveness against Moraxella catarrhalis in acute otitis media, with a presumed bacteriologic eradication rate of 80% at Day 11 and 73% at Day 30.

It is essential to consider local epidemiology, susceptibility patterns, and the specific clinical context to select the most appropriate antibiotic therapy.

From the Research

Antibiotic Options for Moraxella catarrhalis Infections

• Amoxicillin/clavulanate is a broad-spectrum antibacterial that has been shown to be effective against Moraxella catarrhalis infections 5, 6, 7, 8
• All isolates of Moraxella catarrhalis were susceptible to amoxicillin/clavulanate in several studies 6, 7, 8
• Other antibiotics that have been shown to be effective against Moraxella catarrhalis include cefuroxime, azithromycin, ciprofloxacin, moxifloxacin, levofloxacin, erythromycin, and minocycline 6, 7, 8
• However, resistance to certain antibiotics such as ampicillin, cefaclor, and trimethoprim-sulfamethoxazole has been reported 6, 7, 8

Considerations for Antibiotic Selection

• The selection of an antibiotic should be based on the susceptibility of the Moraxella catarrhalis isolate, as well as the patient's medical history and other factors 6, 9
• Pharmacokinetic/pharmacodynamic principles should also be considered when selecting an antibiotic for Moraxella catarrhalis infections 5, 9
• The emergence of antibiotic-resistant strains of Moraxella catarrhalis highlights the need for continued surveillance and monitoring of antibiotic susceptibility patterns 6, 8

Recommendations for Treatment

• Amoxicillin/clavulanate is a recommended first-line treatment for Moraxella catarrhalis infections 5, 6, 7, 8
• Other antibiotics such as cefuroxime and azithromycin may be considered as alternative treatments 6, 7, 8
• Treatment guidelines should be regularly updated to reflect changes in antibiotic susceptibility patterns and other factors 9